# Biofilm Formation in Chicken-Derived Extraintestinal Pathogenic Escherichia coli Alters the Expression of Biofilm- and Virulence-Associated Genes

## TL;DR

This study shows that biofilm formation in chicken-derived E. coli changes gene expression, increasing persistence and virulence.

## Contribution

Identifies specific genes consistently upregulated during biofilm formation in chicken-derived ExPEC strains.

## Key findings

- Biofilm formation upregulates genes like flhC, tolA, qseC, mhpB, and bdcR across all strains.
- Virulence genes eaeA, fimH, ompF, and iss are significantly upregulated in the biofilm state.
- Nutrient-rich media consistently promote rapid biofilm formation in chicken-derived ExPEC.

## Abstract

Background: Extraintestinal pathogenic Escherichia coli (ExPEC) poses significant health risks to poultry and humans, with biofilm formation often complicating treatment by enhancing bacterial persistence and resistance. Understanding the genetic mechanisms underlying this lifestyle transition is crucial for controlling infections. This study aimed to investigate the effect of biofilm formation on the transcriptional expression of specific biofilm- and virulence-associated genes in chicken-derived ExPEC strains. Methods: Biofilm formation conditions for three strong biofilm-producing chicken-derived ExPEC strains were optimized using an orthogonal experimental design (L9(33)), evaluating culture medium, incubation time, and initial inoculum concentration. Biofilm biomass was quantified via crystal violet staining. Subsequently, the transcription levels of 10 biofilm-associated genes and 17 virulence-associated genes were compared between planktonic and biofilm states using Reverse Transcription-quantitative PCR (RT-qPCR). Results: Optimal culture conditions varied among strains, though nutrient-rich media consistently promoted rapid biofilm formation. Transcriptional analysis revealed significant reprogramming in the biofilm state. Among biofilm-associated genes, flhC, tolA, qseC, mhpB, and bdcR were consistently and significantly upregulated across all strains (p < 0.05). Regarding virulence determinants, the expression of eaeA, LT, fimH, ompF, and iss was significantly upregulated (p < 0.05), whereas Sta levels were significantly reduced (p < 0.05). Conclusions: Biofilm formation induces a distinct transcriptional shift in chicken-derived ExPEC, simultaneously enhancing the expression of key genes involved in biofilm maintenance and pathogenicity. The conserved upregulation of flhC, tolA, qseC, mhpB, and bdcR suggests these genes are critical drivers of biofilm development. Consequently, they represent potential targets for novel therapeutic strategies aimed at preventing E. coli infections and eradicating biofilms in clinical and agricultural settings.